Electric furnace



ELECTRIC FURNACE 8. Filed March l, 192

April 15, 1930- electrically Patented Apr. 15, 1930 UNITEDA sra'rris.l

OF SCIHENEOTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A.CORPORATION OF NEW YORK ROBERT M. CHERRY,

'PATENT' oFFicE .ELECTRIC 4 FURNACE My invention relates to electricfurnaces, especially to resistance heating units for electric furnaces,and has for its object the provision of a heating unit which is ruggedin construction, efficient in radiating heat, and which may be easilyremoved from the furnace structure.

For a better understanding of my invention reference may be had to theaccompanying drawings in which Fig. l is a side elevation view of afurnace embodying my invention, and Fig. 2 is asectional View taken onthe line 2--2 of Fig. 1, looking in the direction of the arrows.

-Referring to the drawing, in carrying out my invention in one form Iprovide a furnace structure comprising side and roof walls 11 definingan elongated heating chamber 12, the walls being casing 10. These wallsare preferably formed by. an inner wall-13 made of heat refractory isspaced from inner wall .13 and the space between the casing and innerwall is filled ywith a suitable powdered refractory heat insulatingsubstance, such as a diatomaceous material. AA heat refractory bottom isalso provided. -An opening 12 is provided in one end wall through whichthe charge may be inserted and removed, or if desired the charge 'may bepushed through the heating chamber and removed through a suitableopening prov-ided in the opposite end.4

The furnaceis heated by. means of one or more electric heating units 15mounted in the upper part of the heating chamber and also if desired byone or more heating units 16 in the bottom .of the heating chamber. Inthe elongated furnace shown a plurality of heating units are provided inboth the top and the bottom of the furnace. The units at the top areslidably mounted on suitable brackets so that they may be separatelyinserted and removed from the side of the furnace. As shown, the upperunit 15 adjacent the end ofthe furnace is mounted at one side on abracket 14 secured to the furnace wall, the opposite side of the 'unitbeing supported on a bracket formed by a plate 17 which is secured tothe lower side of a supporting bar provided with an outer metalinsulating bricks. The casing 10 v 18 extending across the heatingchamber and y having its ends secured in the side walls as indicated inFig. 2. This supporting bar 18 may be rigidly secured lto the furnaceywalls or`it may be mountedso that it may be readily removed andreplaced. The bar 18 is made from a suitable heat'refractory material,such as aluminum oxide. It is shown as supported at the center by meansof a metallicl rod 19 extending upward through the roo-f of the furnace.The rod 19 may, however, be dispensed with, or a greater number may beused, depending on the width of the furnace and the weight of theheating units. The plate 17 projects beyond the opposite side of the bar18 and forms a supporting bracket for one side of the next adjacentheating unit, as indicated in the drawing. A plurality ofsupporting'bars 18 may be provided depending upon the number of heatingunits to be supported. heating unit is used, the supporting brackets forboth sides may be secured directly to the furnace wall. j

The heating units 16 in the bottom of the furnace are similar inconstruction to the upper heating units 15 but are mounted in invertedpartments 20'in the bottom of the furnace. These compartments areseparated by walls 21 which form supports for Ithe abutting edges ofhearth plates-23 extending over the lower heating units.v The hearthplates are preferably m'ade of a heat resisting metal, such as 'nicklechromium alloy, as are also In .the event that only a single relationwith respectthereto in 'comvarious other metal parts in the interior ofthe furnace.

Since as Astated above, all of the heating I units are identical, avdescription of one unit Awill be sufficient. A plurality of L-shapedhanger blocks 24 made of a suitable electri- I cally insulatingV lheatrefractory material,

bars 26 are provided for each pair of support- As shown, live cross hooklying in the recess 27. The hook mem` ing bars, one being provided ateach end and three intermediate the ends. The elongated supporting barsand the cross bars' 26 held together by'means of the tie rods 25 thusform a grid shaped framework which may be readily-placed upon or'removedfrom the supporting brackets 14 and 17.

Each hanger block 24 is provided in one side with a triangular recess 27formed with one of'its sides at one end surfaceof the block i. e., atone end of the L and with its apex toward the center of the block. Ahole 28 passes transversely through each block 24 vat l the apex'of thetriangular' recess 27. These' holes and recesses inthe blocks areprovided to receive metallic hook members 29 made of a suitable heatresisting metal, one hook member being secured to each block and eachhook member having a transversely bent end which is inserted in the hole28, they shank of the bers 29 are inserted in the recesses 27 and 28 inthe blocks rwhile the blocks are being assembled and it will be observedthat each hook member is free to swing in its slot 27 on the pivotformed by its transversely bent end lying in the hole 28. The hookmembers are prevented from working out of the holes 28 by the sides ofthe adjacent blocks 24.

The hook members secured to each framework form supports for a heatingresistor 22 which preferably is formed, as shown, from a ribbon ofsuitable resistance heating mate rial, such as a nickel chromium alloy,the ril bon being bent into a plurality of zig-zag, substantiallyparallel lengths or convolutions extending back and forth between theparallel refractory bars of each framework. In the upper heating units,for example, it will 'be observed that the bends joining theconvollutlons pass around the rshanks of the hook members and lie in thehooks in the lower ends thereof. That is, a hook is provided at eachbend of the resistor whereby the resistor is supported. The recesses 27and holes 28 in the blocks 24 are so placed in the blocks that the hookmembers are free to swing in a transverse direction with respect to thesupporting bars formed by the blocks whereby the hook members are freeto swing in the direction of the expansion and contraction of theresistor dueto changes in temperature.

It will beobserved that the bottom heating units 16 are placed ininverted relation with respect to the upper heating units 15, theresistor 22 in this case resting upon the insulating supporting barsformed by the blocks 24 instead of being hung on the hooks 29. The

resistor is positioned laterally and held in serve to close the recess`27 in thel adjacent viffessaasi i block 24. These spacer blocks 30 mayalso be placed between the hanger blocks 24 at diiferent points in orderto lengthen the unit and adapt a certain resistor to diderent sizedfurnaces. Attached to and projecting from some of the cross bars 26 arespacing insulators 31,-which are rigidly attached to the cross bars 26centrally thereof and extend between the pair of lengtlis orconvolutions of the resistor at this point. Attached to the cross bars26 centrally thereof are insulating plates 32 containing slots 33, theseplates eX- tending in the opposite direction from the insulator 31. Thereturn leads of the resistors 22 are brought through these slots in theinsulating plates 32 to one side or the other of the furnace where theyare brought` through the walls in proper insulating bu'shings, notshown. rlh'e other leads 34 of the resistors 22 are shown in F ig. 2 aspassing through suitable insulating bushings 35 in the furnace wall.

In Fig. 2 the right-handside wall of the furnace is shown, as containingremovable it may be desirable to make thesect-ions 36 `integral with theframe structure of the units l5 or 16 so that a unit and a section ofthe furnace wall may be removed or replaced in one piece. Suitable tilemembers 38 are built in the furnace wall to act as a support for thewall when the sections 36 are removed.

Several modilications-may be made without departing from the scope of myinvention. For instance, ledges 14 and 19 of the supporting brackets mayeach be provided with an upward llange, and a downward flange may alsobe provided on each of the refractory bars formed by the hanger blocks24 so that by this flange fitting over the flange on the cooperatingsupporting bracket the blocks will be held more securely on thesupporting brackets '14 and`17, but will still be easily removabletherefrom. Also, return leads of the resistors may pass through bushingsat the back side of the furnace and thus the insulating plates 32' mightbe dispensed with. On the other hand, the return leads of the bottomunits 16 may be brought out along the side of the units through theproper insulators.

Itis to be observed that with my arrangement vthe grid frames from theupper walls of said furnace so as to support their resistors 1nhorizontal relation with the resistors positioned in the bottom of saidfurnace, said l suspending means comprising a supporting bracket"extending across' said furnace for supporting the adjacent edges of eachpair of said grid shaped frames.

2. In an electric furnace, a heating unit comprising a plurality7 ofrefractory L-shaped hanger blocks, means for supporting saidblocks inparallel rows, a metallic'member loosely mounted in and projecting fromone leg of each L-shaped block, a heating resistor supported by saidmetallic members, and means attached to the walls of said furnace onwhich the other legs of said L-shaped blocks are adapted to rest.

3. In a heating unit for electric furnaces, a plurality of refractoryhanger blocks, a` grid shaped framework for holding said blocks in twoparallel rows, a metallic hook member loosely mounted in and projectingfrom each hanger block, and a resistance element supportedby said hookmembers.

4. In a removable heating unit for electric furnaces, a plurality ofrefractory hanger blocks, a skeleton framework for supporting saidblocks in parallel rows, a metallic member projecting from each of saidblocks and pivotally mounted therein, and a sinuous resistance elementsupported by said metallic 5. In a removable heating unit for electricfurnaces, a plurality of refractory hanger blocks, a framework includinga plurality of cross bars for supporting said blocks in paraln lel rows,metalic members loosely mounted in and projecting from said blocks, asinuous heating resistor supported by said metallic members, andinsulating guide blocks attached to said cross bars and through whichpass the terminals of said resistor..

6. In a removable heating unit for electric furnaces, a plurality ofrefractory hanger blocks, a framework including a plurality of crossbars for supporting said blocks in parallel rows, metalic membersloosely mounted in and projecting from said blocks, a sinuous heatingresistor supported by said metallic members, insulating guide blocksattached to some of said cross bars and through which pass the terminalsof said resistor, and refractory spacing members attached to said crossbars and holding the turns of said sinuous resistor spaced from eachother.

' 7. In a removable heating unit for electric furnaces, a plurality ofrefractory blocks, means for securing said blocks together `to form apair of elongated refractory bars, metallic members connecting saidrefractory bars to form a supporting framework, metallic hooks looselysecured to said bars, and a sinuous resistorv shaped into substantiallyparallel length extending between said'bars, said resistor beingsumiorted on said hooks at the junctions of said lengths.

8. In a furnace, an electrical heating resistor, a removable*v frameworkextending across said furnace, and metallic hook mem bers secured tosaid framework engaging and supporting said resistor.

9. In an electric furnace, a heating unit comprising a plurality ofrefractory L- shaped hanger blocks, a grid shaped framework for holdingsaid blocks in parallel rows, metallic hook members mounted in andprojecting from each leg of each L-shaped block, a heating resistorsupportedby said metallic members and mea-ns attached' to the to form asupporting framework, a plurality of metallic hook members pivotallysecured to said refractory members and a heating resistor supported bysaid hook members'.

l1. A heating unit for electric furnaces comprising a plurality ofrefractory members, means for securing said refractory members together,a plurality of hook members pivotallysecured to said refractory membersand a heating resistor secured to said hook members.

l12. A removable heating unit for electric furnaces comprising aplurality of elongated refractory members, means for securing saidmembers together to form a supporting framework, a plurality of metallichook members having transverse end supporting portions secured to saidrefractory members so as to be pivotally movable on said transverse endportions and a heating resistor supported by said hook members, saidresistor extending back and forth between said refractory members.

13. In a. furnace, a framework extending across said furnace andslidably removable from a side wall of said furnace, metallic hookmembers pivotally secured to said framework, anda heating resistorsupported by said hook members extending back and forth between saidhook members.

In witness whereof, I have hereunto set my hand this'29th day ofFebruary, 1928.

, ROBERT M. CHERRY.

